[cbcollect_info] Don't create new session for tasks.
[cbcollect_info] Don't create new session for tasks.

Just creating a process group achieves all the same objectives. And
it's more logical to do so, because we don't care about stuff like
controlling terminal.

Change-Id: If8932c21304429c47f4a4da15a405248c89237f2
Reviewed-on: http://review.couchbase.org/71673
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server